Do polish passport holders need a visa to work in the UK?

NO they don't. They can live, study and work freely in any capacity including Contract, Freelance, Permanent, Temporary, Part-Time, Interim, etc. From Home Office website: If you are a national of a country in the European Economic Area (EEA) you do not need permission to work in the United Kingdom. The EEA includes these countries: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Liechtenstein, Lithuania Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, United Kingdom.